Such a device is known from German Pat. No. 1,635,899. Its storage drum is rotationally drivable. The sliding disc is mounted on the end of the drum, in the vicinity of which the thread is delivered, and comprises arms extending outwardly through longitudinal slots in the drum wall. It is mounted so as to rotate with the drum and can be tilted about a pin passing transversely through the drum axle. A power storage element urges the sliding disc into the inclined position and the angle of inclination is dependent on the size of the thread supply on the storage drum. A microswitch can be actuated depending on this angle of tilt and in turn controls the winding drive, i.e. the drive for rotating the storage drum. By way of its control member which is in contact with a flange on the surface of the sliding disc remote from the drum, the microswitch acts simultaneously as a power storage element.
With a device of the described type a substantially smaller difference between the minimum and maximum thread supply occurs when the drum diameter is small and the microswitch is actuated with the angles of tilt being the same as with drums of large diameter, which results in frequent switching on and off of the winding drive. If a greater deflection is allowed for the minimum thread supply to compensate, i.e. a substantially greater incline for the tilted sliding disc, this leads to constructional problems. The slits through which the fingers of the sliding disc project must be lengthened, the fingers must also be made longer and thinner to ensure their smooth movement through the slits. However, when the angle of tilt is small, the longer fingers of the sliding disc then project further outwardly beyond the drum diameter. Also the free space on the outside of the drum is reduced when the angle of inclination of the disc is great. There is the danger that the wind-on thread may no longer come into contact with a free surface. Moreover, space must be provided on or outside the storage drum for the half which is pivoted upwardly when the angle of inclination of the sliding disc is great, thereby increasing the overall height of the device. This is not always desirable, particularly in the case of sewing machines where space for the necessary device must be kept to a minimum so as to allow unrestricted working.
The problem for the invention is to provide a thread storing and feeding device of the type described at the beginning of the specification, which enables adequate and positively controlled storage of thread by simple means and in this connection has relatively small dimensions.
This problem is solved in accordance with the invention by mounting the sliding disc on a pivot lever, of which the end directed away from the sliding disc is tiltably mounted at a distance from the storage drum axis at least approximately equal to the drum radius.
The mounting arrangement outside the area of the drum enables the sliding disc to be moved in an almost straight line axially to the drum when the thread supply changes. As a result the tilting of the sliding disc does not cause any increase or variation in space requirement. The arrangement of a practically only axially movable sliding disc in the drum area is in constructional terms simpler than that of a tiltable disc. In this connection it is unimportant whether the winding drive acts directly on the storage drum causing it to rotate conjointly with the sliding disc, or whether the storage drum and sliding disc are stationary and the winding drive moves a take-up element around the drum. The path of the thread being taken up onto the storage drum is not obstructed by the disc, irrespective of the size of the thread supply. Another important advantage of the device according to the invention is that no power storage element is required for the sliding disc, but its movement relative to the storage drum axis subject to the thread supply is determined by its own weight and that of its support.
The pivot lever advantageously actuates the device for controlling the winding drive. The position of the pivot lever is always determined by the position of the sliding disc. The control device, which does not have to fulfill an additional function as a power storage means, can therefore cooperate with any desired range of the lever. Its spatial arrangement is therefore adaptable within broad limits to the other constructional factors of the thread storing and feeding device.
The section of the pivot lever remote from the pivot bearing extends advantageously beyond the center of the storage drum. The sliding disc can then be suspended from the pivot lever at least on either side of the drum axle, i.e. symmetrically thereto, which produces positive guiding. The pivot lever is lengthened without a particularly large amount of space required, and particularly without the distance between the drum axle and pivot bearing becoming relatively great. Its free end thereby obtains a great and almost linear path of deflection which affords advantages particularly in cooperating with the control device.
The lever can be associated with a stop member in the housing which limits the tilting movement of the lever in both directions. The limits of movement of the sliding disc relative to the storage drum and therefore the desired minimum or maximum thread supply can be determined by adjusting this stop member.
The stop member is advantageously provided in the vicinity of the pivot lever end remote from the bearing, which is the point of maximum lever deflection.
In a preferred embodiment the pivot lever is designed substantially as a plate having a width approximately equal to the diameter of the drum. The lever is therefore stable, absorbs evenly the forces transmitted thereto by the sliding disc and ensures a steady and positive pivoting action adapted to suit the thread supply. The fastening elements are provided with sufficient area for the symmetrical fitting of the sliding disc.
Simple and economical mounting of the pivot lever is achieved by the fact that the lever acts as a rocker and has grooves or recesses which extend around corresponding projections on the housing.
For a device comprising a storage drum rotatably driven by the winding drive, the pivot lever can be connected to a bearing plate arranged between it and the sliding disc by retaining elements and the bearing plate to the sliding disc by rotary bearings. The bearing plate both allows the rotary bearings for the sliding disc to be mounted relatively remotely from the pivot lever, even inside the drum, and supported in the proximity of the drum axle relative to which they must be vertically movable. Such statically advantageous mounting of the rotary bearings directly on the pivot lever replaces the arrangement of the rotary bearings for the drum axle and/or its supports on a housing bottom between the lever and the drum. The bearing plate furthermore permits the use of simple retaining elements, for example screws, since they make possible a connection between two parallel plates inclined towards one another.
In a preferred embodiment the sliding disc comprises an edge extending around the upper drum edge of U-shaped cross section and having fingers forming the free U-shaped side and engaging in an inward direction in longitudinal slits in the storage drum.
In the area of its end remote from the bearing, the pivot lever can comprise a nose projecting laterally in its main plane and cooperating with a microswitch provided in this section. The microswitch can therefore be mounted laterally of the drum axle in the driving member, etc. without adversely affecting operation.